Recently, an energy-information technology (IT) fusion technology has increasingly attracted considerable attention. The energy-IT fusion technology is a technology of fusing a fast developing IT technology into the conventional energy technology. An example of the energy-IT fusion technology is a wireless power transfer (WPT) technology. Wireless power transfer is a technology of supplying power to electric instruments in a wireless fashion instead of using the conventional power cable. The wireless power transfer technology has an advantage in that an electric home appliance can be charged in a wireless fashion without connection between the electric instrument and an electric outlet or a charging device via a power cable. For this reason, research has been actively conducted on the wireless power transfer technology.
Examples of the wireless power transfer technology which have been commercialized or are under research include a magnetic induction type wireless power transfer technology and a magnetic resonance type wireless power transfer technology. The magnetic induction type wireless power transfer technology uses a magnetic induction phenomenon between two coils. In the magnetic induction type wireless power transfer technology, it is possible to transmit power of several W within a distance of several mm to several cm. The magnetic induction type wireless power transfer technology has been applied to a traffic card, a wireless shaver, an electric tooth brush, etc.
On the other hand, the magnetic resonance type wireless power transfer technology is a technology of transferring power based on resonant coupling at a resonant frequency. In the magnetic resonance type wireless power transfer technology, it is possible to transmit power of several tens of W within a distance of several m. Transfer efficiency is affected by a quality factor (Q) value of a resonator.
Meanwhile, many mobile devices which have been recently placed on the market include a near field communication (NFC) module for NFC communication. NFC is a communication technology of transmitting and receiving data within a distance of approximately 10 cm using a band frequency of 13.56 MHz. The NFC module is mounted in a mobile device. The NFC module is used in various applications, such as user authentication, identification cards, credit cards, mobile tickets, and mobile coupons.
Meanwhile, an NFC antenna (coil) is necessary for NFC communication. The NFC antenna includes an NFC reader antenna and an NFC tag antenna, which are separately provided. In a case in which the NFC antenna is realized in a real mobile device, an integration type dual antenna structure, in which the NFC reader antenna and the NFC tag antenna are integrated to have a stacked structure, is used.
Also, an additional wireless power transmission antenna (coil) is necessary for wireless power transmission. In order to simultaneously support an NFC communication function and a wireless power transmission function in a mobile device, therefore, it is necessary to mount antennas together corresponding to the respective functions in the mobile device. In this case, an antenna installation space is limited depending upon the size of the mobile device. That is, the antenna installation space is very small and narrow. Also, the size and thickness of the mobile device are increased due to such two kinds of antennas.
For this reason, there is a high necessity for a technology that is capable of minimizing a necessary antenna installation space although both the NFC antenna and the wireless power transmission antenna are mounted in the mobile device. In connection with this matter, U.S. Patent Application Publication No. US 2010-0194334 discloses an invention entitled “RETROFITTING WIRELESS POWER AND NEAR FIELD COMMUNICATION IN ELECTRONIC DEVICES”. The invention disclosed in U.S. Patent Application Publication No. US 2010-0194334 relates to a power circuit for wireless power transmission and near field communication. An electronic device having the power circuit includes a back housing having a wireless power receiving antenna and a conversion circuit. U.S. Patent Application Publication No. US 2010-0194334 discloses that the wireless power receiving antenna may be used to perform a wireless power transmission function and an NFC communication function. However, detailed constructions to simultaneously perform the wireless power transmission function and the NFC communication function are not disclosed.